Plate nuts or tinnermans?

Before long I am going to be fabricating my tank lids and also mounting my fiberglass wing tips to my experimental wings. I see Piper calls for tinnermans for the tank lids. Anyone switch this out to plate nuts? What are the pro's and cons to plate nuts (aka anchor nuts) vs tinnerman? Which plate nuts are the best to use (nylon or all metal)? They nylon buggers are expensive.

Thanks for any advice,

Bugs

nut plates front and back, tinnermans on the sides (ribs)